Stainless steels are used in an array of applications where their ability to take on colour is of
aesthetic value. Although thermal colouring (heat tinting) is known, particularly in terms of its effect
on welds, the surface development of thermally coloured stainless steel has not been considered in
detail. This paper demonstrates the colour development of a bright annealed 304 stainless steel
with time at temperature. The colour development has been quantified using colour spectrophotoscopy
and the colour related to the growth of surface oxide features by scanning electron
microscopy and the chemical profiles by X-ray photoelectron spectroscopy (XPS). There is a clear
development of both the oxide thickness and chemistry, with increasing time with small nodules
being the main features seen across the surface of the samples with time. The oxides have been
shown to comprise of an outer iron rich oxide and an inner chromium/iron spinel layer.